Unique Three-Year Data Demonstrating Long-Term Efficacy and Safety
of Raptiva in the Treatment of Psoriasis Published in the British
Journal of Dermatology

GENEVA, Switzerland, May 5, 2008 – Final results of the first
three-year prospective efficacy and safety study in
moderate-to-severe chronic plaque psoriasis were recently published
in the British Journal of Dermatology1. They demonstrate the
sustained safety and efficacy obtained with Raptiva®
(efalizumab) in the long-term three-year therapy of this chronic
autoimmune disease.

The data show that Raptiva® therapy had a sustained effect in
those patients who responded to the initial 12-week treatment (82
%). A 75 % improvement in the disease, as measured by the standard
Psoriasis Area and Severity Index (PASI) score (PASI-75), was
achieved in 73 % of responders (as-treated analysis) after three
years of continuous therapy2. Raptiva® was generally well
tolerated during the treatment period of up to three years.

“No efficacy and safety studies of similar duration for
biological psoriasis treatments have ever been published. The
long-term use of traditional therapies may be limited by
inconvenience, as in the case of phototherapy, or increased
toxicities, for example with ciclosporin or methotrexate,”
said study investigator Craig L. Leonardi, MD, Clinical Professor
of Dermatology at Saint Louis University. “Efalizumab
demonstrated sustained long-term efficacy and a favorable safety
profile in this three-year trial. These features make it
appropriate for continuous, long-term treatment of plaque
psoriasis.”

“We see a positive benefit-risk-profile for Raptiva®. The
results of this unique study indicate the efficacy of Raptiva®
in this indication as well as its stable long-term safety
profile,” added Anton Hoos, MD, Merck Serono’s Head of
Global Development. “This is important and reassuring
information for chronic psoriasis patients and their physicians who
wish to manage the disease with continuous treatment.”

The objective of the study was to evaluate the efficacy and safety
of long-term, continuous Raptiva® therapy in patients with
psoriasis. This open-label, multicenter Phase III trial enrolled
339 adult patients with moderate-to-severe chronic (? six months)
plaque psoriasis. During the initial three-month phase, patients
received Raptiva® by subcutaneous injection (2 mg/kg/week). The
second phase was a long-term observational period: Patients
achieving at least 50 % improvement in PASI score (PASI-50) were
eligible to receive Raptiva® (1 mg/kg/week) for up to 33
months; patients who had a relapse during months 4–15 ended
participation in the current three-month segment and started the
next segment at an escalated dosage of 2–4 mg/kg/week. The
final three-month treatment period (months 34–36) was an
optional transition period for patients who completed the 33-month
segment before Raptiva® became commercially available.

Of the 290 patients who entered the observational period, 146
patients completed up to 33 months of Raptiva® treatment and
were included in the as-treated analysis. A total of 108 patients
received up to three years of Raptiva® therapy during the study
(included in as-treated analysis). After the first three months of
therapy, 82 % of all patients (n=339) had achieved PASI-50 or
higher (41 % PASI-75, 13 % PASI-90). After three years of
treatment, the as-treated analysis (n=113) resulted in a response
rate of 73 % for PASI-75 (40 % PASI-90).

Raptiva® was generally well tolerated throughout three years of
continuous treatment, with no evidence of cumulative or end-organ
toxicity. Common adverse events (? 5 % of patients in any
three-month segment) during long-term treatment included increased
cough, rhinitis, sinusitis, and nonspecific infection (e.g. colds).
There was no increase over time in the rate of those common adverse
events. Likewise, no novel adverse events or increase in the
overall incidence of adverse events or serious adverse events was
noted over time. The relatively small size of the cohort limits the
conclusions that can be drawn regarding rare events. A low
proportion of patients (? 3.1 %) withdrew due to an adverse event
during each three-month treatment segment of the observational
period.

Footnotes
1C. Leonardi et al., “Efalizumab: results of a 3-year
continuous dosing study for the long-term control of
psoriasis”, British Journal of Dermatology 2008, 158,
1107-1116.
2All long-term efficacy claims refer to responding patients
(“as treated” analysis). Only the patients who remain
on therapy are taken into account, not those who discontinue
treatment due to an adverse event, lack of efficacy, or any other
reason.

About Raptiva®
Raptiva® (efalizumab) is a humanized therapeutic antibody
designed to selectively and reversibly block the activation,
reactivation and trafficking of T-cells that are critically
involved in the psoriatic skin inflammation. Raptiva® is
designed to be administered once weekly via subcutaneous injection
and can be self-administered by patients at home. Raptiva®
received EU approval for the “Treatment of adult patients
with moderate-to-severe chronic plaque psoriasis who have failed to
respond to, or who have a contraindication to, or are intolerant to
other systemic therapies including ciclosporine, methotrexate and
PUVA”. Common adverse events observed with Raptiva®
include headache, infections (e.g., common cold), chills, pain,
nausea, asthenia (weakness), and fever, which usually diminish
after the initial doses. For complete information on the safety
profile of Raptiva®, the patient information leaflet should be
consulted.

Raptiva® safety data have now been accumulated from ten years
of clinical development and post-marketing experience in psoriasis
patients. Raptiva® is a medicinal product subject to medical
prescription. Treatment with Raptiva® should be initiated by a
physician specialized in dermatology. The Marketing Authorization
Holder of Raptiva® in the European Union is Serono Europe Ltd,
an affiliate of Merck Serono S.A. The full Summary of Product
Characteristics (SPC) for Raptiva® is available on
http://www.emea.europa.eu/humandocs/Humans/EPAR/raptiva/raptiva.htm

Merck Serono has the rights to develop and market Raptiva®
worldwide outside of the United States and Japan. To date,
Raptiva® is available in 65 countries, amongst them many
countries in Europe, Latin America, Asia as well as Australia and
Canada. Raptiva® is licensed from Genentech, Inc., and
Genentech retains development and marketing rights in the United
States, where Raptiva® has been available since November
2003.

About Psoriasis
Psoriasis is a T-cell mediated disease, which is characterized by
abnormal cell growth of keratinocytes and chronic inflammation
clinically visible as thick, red, scaly, inflamed patches and
plaques. Plaque psoriasis, the most common form of the disease, is
characterized by sharp-edged inflamed patches of skin ("lesions")
topped with silvery white scales. Psoriasis can be limited to a few
spots, typically knees and elbows, but can also involve extensive
areas of the body. Although it is highly visible, psoriasis is not
a contagious disease. While there are a number of medications that
may help control the symptoms of psoriasis, there currently is no
known permanent cure.

About Merck Serono
Merck Serono is the division for innovative prescription
pharmaceuticals of Merck, a global pharmaceutical and chemical
group. Headquartered in Geneva, Switzerland, Merck Serono
discovers, develops, manufactures and markets innovative small
molecules and biopharmaceuticals to help patients with unmet
medical needs. Its North American business operates in the United
States and Canada as EMD Serono.

Merck Serono has leading brands serving patients with cancer
(Erbitux®), multiple sclerosis (Rebif®), infertility
(Gonal-f®), endocrine and cardiometabolic disorders
(Glucophage®, Concor®, Saizen®, Serostim®), as well
as psoriasis (Raptiva®).
With an annual R&D investment of around € 1bn, Merck
Serono is committed to growing its business in specialist-focused
therapeutic areas including neurodegenerative diseases, oncology,
fertility and endocrinology, as well as new areas potentially
arising out of research and development in autoimmune and
inflammatory diseases.

About Merck
Merck is a global pharmaceutical and chemical company with total
revenues of EUR 7.1 billion in 2007, a history that began in 1668,
and a future shaped by 31,681 employees in 60 countries. Its
success is characterized by innovations from entrepreneurial
employees. Merck's operating activities come under the umbrella of
Merck KGaA, in which the Merck family holds an approximately 70%
interest and free shareholders own the remaining approximately 30%.
In 1917 the U.S. subsidiary Merck & Co. was expropriated and
has been an independent company ever since.